« Could We Run Modern Society on Human Power Alone? | Main | How to Run the Economy on the Weather »

Comments

Feed You can follow this conversation by subscribing to the comment feed for this post.

Angus

(1)

Fantastic article Kris, thanks.

One idea that is not explored is that of combining approaches to energy. For example, if regions have some storage, and some ability to transmit energy to other regions, and some ability to perform demand management, then there will be (I think!) far fewer days of shortfall.

The reason is that the interconnectors can then be sized to average (demand-reduced) consumption, rather than peak consumption, and storage can be sized for a shorter period because power can be brought in from further away at the reduced rate.

Hope that makes sense, Angus

Marcos Belançon

(2)

I would like to add something to the discussion. It is not necessary to think about the storage, because we don't have a technology for photovoltaics for example that could be scaled up to our needs. The back contact of common PV is made of silver. 25kg per MWp. This means that today we already use 10% of the silver extracted every year to fabricate photovoltaics. And if we keep the actual production rate, in about 20 years the installed capacity will not grow anymore. We will be replacing the older ones. Wind is not so different.

Hilton Dier

(3)

Part of the problem is that we (the U.S.) waste so much energy. The average European uses about 60% of the energy of the average American. With real effort we could cut our usage in half.

Hydroelectric is part of the solution. Hydro output varies over hours and days rather than minutes and is much more predictable. It provides about 6% of our present production. Make that 12% if we stopped wasting so much.

The latest and most promising storage method is actually quite simple. A company called ARES is building a MW scale storage system that is an electrically powered train loaded with stone on a track that goes up the side of a mountain. It's all early 20th century technology, aside from the control system. No exotic batteries necessary. They claim an 80% round trip efficiency, which is roughly that of a battery.

But yes, a demand side strategy is the best. We should all have electric meters on the *inside* of our houses, giving us our present and historical use, present cost of electricity, and predicted future cost. That would allow us to make informed decisions about use.

kris de decker

(4)

Correction. I deleted the following sentence because it is wrong: "Energy storage also assumes an oversizing of the renewable power capacity, otherwise there would never be a surplus of electricity that could be stored for later use."

Keith H. Burgess

(5)

I totally disagree. This is more to do with the ability to store the power than producing it, & it is about how much people use & think they need to use. People need to get a grip. We have been off grid for over 40 years. We have a relatively small solar power set up. We have a 24 volt battery bank converted to 240 volt AC. The main item we power is or fridge freezer, & we lived for over 20 years without any electricity at all.
Keith.

kris de decker

(6)

@ Keith

The article is not talking about off-the-grid systems. In fact, an off-the-grid system is a good example of a system that adjusts demand to supply to a certain degree. Battery storage is costly so it's usually limited to a few days of reserve at most. During longer low power periods, off-the-gridders adjust demand to supply. They have no other choice.

zmau

(7)

You missed one important concept in the system. Prices. Price is very strong piece of information which helps to adjust demand to supply.

So, when supply is low, prices should go up (that's exactly what happens on all free markets all over the world), and people will spend less. So there will probably be no need for real restrictions.

Also, overall higher energy price will surely reduce overall consumption, and that's really not a problem, because a lot of cheap energy is just wasted anyway.

John Weber

(8)

Many materials used in our industrial world require energy from mining to manufacturing for processing and transportation. The energy for some of these products is in the form of high temperatures – 2000° F (nearly 1100°C).
These processes run 24/7 365 days.

There are proposals that solar and wind energy collecting devices can provide the energy to maintain the industrial world. To look at this possibility, solar electric panels, wind turbines and concentrated solar installations in the form of parabolic trough collectors (PTC) have been assessed.

The energy requirements in 2010 for the following essential components of our industrial world are provided: steel, aluminum, chromium, copper, manganese, cement and glass. This energy would be mining, processing and transporting to name some. Other important components of the industrialized world such as nickel and cobalt are not considered because they are part of the high temperature processing of other ore metals.

The kWh output and area required for installations of solar electric panels, wind turbines and PTC has been researched. This then is divided into the energy (exajoules converted to kWh) required for global production of each material in 2010.

NEEDED
121,214.45 Square Miles of Solar Electric Collectors
257,472 square miles and 2,807,276 Wind Turbines
77183.4 square miles of PTCs
There are many other critical components of our global industrialized world that require industrial heat (lead, silver, tin, food processing) that are right at the top heating limit of solar devices. They must also be included in an all “renewable” future. If only half of important materials were provided, what would our world be like?

IN AN INDUSTRIALIZED SOCIETY, IT FALLS TO THE PROMOTERS OF A FUTURE FOR “RENEWABLE”
ENERGY TO SHOW HOW THESE ESSENTIAL
MATERIALS AND SO MUCH ELSE CAN BE PROVIDED.

See maps, images and calculations at:
http://sunweber.blogspot.com/2017/08/heat-for-tomorrow-many-materials-used.html

John Weber

(9)

ORE GRADES
This paper quantifies, on a global level, the relationship between ore grade and energy intensity. With the case of copper, the study has shown that the average copper ore grade is decreasing over time, while the energy consumption and the total material production in the mine increases. Analyzing only copper mines, the average ore grade has decreased approximately by 25% in just ten years. In that same period, the total energy consumption has increased at a higher rate than production (46% energy increase over 30% production increase).
Decreasing Ore Grades in Global Metallic Mining: A Theoretical Issue or a Global Reality?
http://www.mdpi.com/2079-9276/5/4/36

John Weber

(10)

There are multiple questions that a realistic assessment of the future of these devices requires. Each of these questions asks about the future of “renewable” devices.

First and foremost:
What do we need the energy for?
Not, why - what do we want this electricity for.
This must be one of the mantras for survival now and tomorrow.

When it comes time to replace these devices:
Where will the energy and resources come from?

To replace components of these systems:
Where will the energy and resources come from?

As we need to manufacture the tools and toys we want the electricity for:
Where will the energy and resources come from?

Will we sequester/store the energy to provide for these future needs?
How will we do that?

OR

Will dedicated devices be built simply to facilitate replacement of devices and their auxiliary parts (inverters, controllers, fans)?

Who will manage these dedicated devices?

What will stop society from using this sequestered energy?

Will the need to protect this sequestered energy create an even more constrained and draconian social environment?

How will this electricity be equally shared globally compared to the present unequal energy availability?

How will we mine and transport all these raw resources:
the basic material for fabrication, the actual devices, the various auxiliary equipment, the tools and the toys?
More at: http://sunweber.blogspot.com/2016/11/the-energy-in-our-future.html

Jan Steinman

(11)

It's about time someone said this!

While the politicians continue to recite, "Our life-style is not negotiable."

Darkest Yorkshire

(12)

I'm becoming increasingly concerned about the capacity of renewables but this post misses a few things that may make the future less bleak.

Demand response is widely used in industry and is growing. Companies get paid a lot of money to crank up operations when there's too much power in the system and to turn off consumption and fire up their backup generators when there's too little. https://www.flexitricity.com/en-gb/

Those sorts of generators can back up renewables and can themselves be fueled by renewable or industrial waste gasses that have to be got rid of somehow. It doesn't have to be a single-use fossil fuel infrastructure. https://www.clarke-energy.com/news/ (see particularly 'Gas Types' and 'Power' sections.

None of your sources on energy storage included the best one - liquid air energy storage. http://www.liquidair.org.uk/about-liquid-air It piggybacks on the industrial gas business so needs far less new technology and infrastructure. It also has several uses. http://dearman.co.uk/ In addition to the listed uses, another option is to separate the air into oxygen and nitrogen. This uses more energy but the nitrogen can then be used for nearly everything liquid air can, except where there is a suffocation hazard. The oxygen has many uses but one of the most interesting is to run industrial furnaces in oxyfuel mode (particularly flameless), which results in fuel savings and a better end product.
http://www.praxair.com/industries/metal-production/oxygen-enhanced-combustion
http://www.lindegaspr.com/internet.lg.lg.pri/en/images/Flameless%20oxyfuel%20for%20more%20production%20CO2%20NOx%20SuE%200708811_10828.pdf

Also, I love how the Zakeri article lists the options to decouple pumped hydro storage from geographical restraints and they get progressively weirder - "water filled balloon under pressure caused by sand". That sounds like an insane nineteenth century patent application from the enthusiastic heights of the age of invention. Or some world-changing project the Bolsheviks planned but never quite got round to. :)

Keith Pickering

(13)

You've hit the nail on the head here in many ways. It's not just energy, it's EROI as you have correctly shown; and VRE (solar and wind) are marginal on their own, but require much more energy input to make them viable at high grid penetrations. A recent paper by Weissbach et al. has broken this down more explicitly, looking at both EROI with and without required storage, and the economic limits under each. The paper assumes pumped hydro for storage, which is still far and away the cheapest storage medium, although it is geographically limited. See:
http://homepages.uc.edu/~becktl/shaka-eroi.pdf

This is why many of us (although perhaps not on this site) see substantial increases in nuclear power as the last-best hope of building a carbon-free civilization.

Andrew Streit

(14)

I believe that this article is the precursor to the future, one that as the generation who 'tamed nature' many will find abhorrent. Fossil fuels allowed us to ignore everything we learned in the past millennia and build the same house in Minnesota as Nevada or New England. Burn baby burn has been our mantra and one that purely on the engineering feat I am proud of. We proved we could do something, now we have to do it smarter and with centuries in mind not fiscal quarters or shareholder returns but survival. At some point any article which says "expensive" I am going to ignore. If fossil fuels will eventually run out, (a common theme if you believe the earth is round) then investment in fossil fuel replacement is infinitely cheaper than re-investing in a dying industry. Philosophically, pragmatically and sustainably a society based solely on profit is fading so how do we transition to an economy that is built on scientific principles and societal preservation and expansion?

Tilman Keding

(15)

As already partly mentioned in comments above, I'm missing other types of renewable energy in the article... hydropower and biogas especially. These are more stable and can, depending on the type of plant, be used for energy storage.

The energy market (in europe) is already partly regulating itself today by adapting prices to demand and availability of energy, up to negative prices, when there is too much power available. Demand side management, where industries with high energy demand can give the energy supplier the option to switch off their non time-critical machinery when little power is available, is already in use today (in Germany for industrial power use of >50MW).

Depending heavily on the the available resources (wind, sun, water, biomass), studies show that 100% renewable energy is definitely possible without big increas in storage, in Germany for example if the grid connections between areas of high production and high demand are improved: https://www.energiesystemtechnik.iwes.fraunhofer.de/content/dam/iwes-neu/energiesystemtechnik/de/Dokumente/Studien-Reports/2014_Roadmap-Speicher-Langfassung.pdf

Still, to not turn the whole landscape in energy production spaces, it would be great to not only adapt energy demand, but also reduce it.

George Smiley

(16)

Some of the calculations look specious to me, especially the manufacturing ENERGY payback times for renewable infrastructure. Fifteen years for a solar panel? A home 300 watt panel costs about $300 and it will take 7-15 years to pay the capex back including its share of the whole system; total manufacturing COST, installation, inverter, wiring, retail mark-ups and EVERYTHING. I suggest the actual energy component consumed in producing this item is negligible. I can unmake it by melting it to a primordial white hot blob in an inefficient little home-made gas powered fan-forced furnace with $25 worth of LP gas and most of the heat just blows on past. I won't bother looking up the kilojoules from that 20 kg. of propane, but I suggest a week's panel output, say 1.5 KWh per day stored in batteries would outdo the LP and vaporize the panel using a plasma cutter for about $1 worth of energy. Which also suggests that high temperatures from renewables may be difficult in terms of steady baseload power as required by a continuously operating smelter but it is in no way out of the question.

Brian Mallalieu

(17)

An interesting & obviously well-thought through article, but two other points that could be considered:

1. Macro-supergrids (i.e. worldwide)could utilise the fact that the sun does not 'disappear' for 12+ hours, but merely transfers to the opposite hemisphere, and even winds also vary in intensity & time across the world.

2. Other renewables (unmentioned) are available e.g. biomass, AD, geothermal etc. which can contribute.

J.C.

(18)

The answer is nuclear. We have "magic" available to us, but are still operating based on unjustified fear.

John McGinnis

(19)

A thorium salt reactor has just been restarted. Thorium reactors could provide the baseload metrics needed by society.

kris de decker

(20)

Discussions at Resilience & Treehugger

http://www.resilience.org/stories/2017-09-14/how-not-to-run-a-modern-society-on-solar-and-wind-power-alone/

https://www.treehugger.com/green-architecture/why-wind-and-solar-wont-save-us.html

deadrody

(21)

Adjusting demand..... LOL!!! You do realize that there are plenty of people, damn near 50%, if not more (probably a lot more_, including hardcore environmentalists that - if told, well, you can only run half the appliances, lights, etc. that you want, so you can have true 100% renewable energy - have no real interest at all.

People who realize 100% renewable energy as well as "global warming" are pipe dreams are really not interested in curtailing their electricity usage to support a mythical "100% renewable energy" grid.

I mean, I appreciate the time taken to illuminate just how unrealistic "100% renewable energy" really is. But at what point do we start to realize, there is no money for ANY of that. No a super grid, not 3-5 times the renewable generation capacity, not any kind of scale-able energy storage. None of it. Like I said - pipe dream.

William Thorpe

(22)

@John Weber - there has been some good work done on using solar furnaces for industrial heat, smelting etc. Some interesting examples even on this website. They can easily get the temperatures required for most processes (there is some limit, but it's well above 3,000 C).

The issue of course is that most industry currently is situated in countries without so much solar resource. It might be that in a solar powered economy, industrial processing will need to move to sunnier regions in order to directly access the availability of solar heat. That could have interesting geopolitical consequences.

kris de decker

(23)

@ J.C & John McGinnis (#18, #19)

Concerning nuclear, I'm prepared to make a compromise. Lower the electricity use to the level of what the already operating atomic plants produce and I agree. However, if you plan to build new power plants to match supply to demand at all times, you're running into the same problems: it takes too much resources, money and time to go nuclear at such a scale. And atomic plants are (more or less) fine as long as there is peace, and as long as there's money to maintain them.

@ Brian (#17), Tilman (#15), Hilton (#3)

The choice for solar and wind energy only is based on the fact that these are -- by far -- the renewable energy sources with the largest potential. Hydropower and biomass could only be scaled up with devastating consequences. You could turn every mountain range into pumped storage power plants, but that means flooding nature and villages.

Counting on biomass is of course a great risk for deforestation. Wind and especially solar energy (the mother of almost all other renewable energy sources) are much less problematic in this sense. We have to be careful not to harvest too much wind (climate change!) but we are still far from that. And for solar energy, there are no such issues at all.

If we're going to run society on renewable energy, sun and wind will be our best chance.

kris de decker

(24)

@ George (#16)

I'm not sure what you mean. I based my calculation for solar PV panels on an energy payback time of 2 to 4 years, depending on location. However, these numbers imply that all electricity produced by a solar panel is effectively used. From the moment you start curtailing solar energy, it will take more time before a solar panel generates the energy it took to produce it.

@ Brian (#17)

Building even larger supergrids to take advantage of even wider geographical regions, or even the whole planet, could make the need for balancing capacity largely redundant, that's right. However, this runs into the same problems and could only be done at very high costs and increased transmission losses.

The transmission costs increase faster than linear with distance traveled since also the amount of peak power to be transported will grow with the surface area that is connected. Practical obstacles also abound. For example, supergrids assume peace and good understanding between and within countries, as well as equal interests, while in reality some benefit much more from interconnection than others. See reference 22.

@ zmau (#7)

Using pricing to regulate energy demand is not that easy. First of all, there's many people, even in the industrialised world, who can't afford to pay their energy bills. Second, to make it work, price differences have to be quite large, considering the relatively low price-elasticity of electricity demand. If you would have large price peaks that reflect the variable supply of renewable energy, leaving the refrigerator on when you leave the house on a windless night might ruin you. Maybe it's a good idea for industry: large factories pay much lower electricity prices than households.

kris de decker

(25)

@ Darkest Yorkshire (#12)

I looked into this "Flexitry" company you mentioned. If I understand the concept well, it's totally the opposite of what I mean. They use backup generation capacity from factories (often diesel generators) to match supply to demand in periods of low renewable power generation.

They write that they make it "possible for a much larger volume of variable renewable generation to be absorbed", but their approach doesn't lower the energy demand in times of short supply. It basically provides a balancing capacity of fossil fuel power plants.

Darkest Yorkshire

(26)

Flexitricity's website doesn't do as good a job of explaining what they do as it used to. I think they emphasise on-demand generation because more businesses are interested in that beecause it doesn't interrupt production and gets another use out of the generators they already have. But both the Frequency Response and STOR services can work either by turning on generation or turning down demand. Footroom turns up consumption to absorb renewable surpleses.

Most of the current generators run on diesel but gas engines could run on natural gas, biomethane, syngas or a few industrial waste gases. In my previous comment on oxyfuel for industry I didn't mention that it also allows carbon monoxide to burn faster and so be used not just in low temperature boilers but in high temperature furnaces and gas engines as well. So syngas becomes more useful when separated into hydrogen and carbon monoxide.

But then there is the problem of what to use renewable gases for, as even at maximum production there isn't enough to go round. The choices are domestic heating, on-demand generation, transport fuel or industrial use (biomethane can do any of them, syngas is poisonous so is more limited). And the potential in any one of these areas is limited. Claims for domestic heating vary from 50-100% and for electricity 1% of demand (but available whenever needed). I don't know if anyone has tried to calculate how much industrial gas demand can be met sustainably.

The transport potential I read was about 15%, so enough to take a decent chunk out of bus and truck consumption. The potential of using liquid methane as a transport fuel has increased recently along with the development of the Dearman engine. It was realised that it releases energy in two stages - when it expands from liquid to gas and when the gas burns. If an engine is designed to take advantage of both stages, liquid methane's energy density rises considerably.

Even with these options gases are as serious a renewable crunch point as electricity and liquid fuels.

I've always been against nuclear but have been looking at the claims for fast neutron reactors. They can be fuelled on anything - uranium, plutonium, thorium, nuclear waste - and can stretch supplies for thousands of years. They have liquid cores so can't melt down. The fuel is reprocessed in the same building with good fuel put back in the reactor, medical and industrial isotopes removed, and what is left is only radioactive for 300 years instead of 80,000+. These designs seem to solve an awful lot of problems, so what are the arguments against them?

Antoine BL

(27)

Fantastic article as always.

However it talks of the future of the electricity grid only and not of the gas network which provides a big part of our energy consumption.

One of the solutions that was not explored here lies in the complementarity between these two networks. Negawatt is a french association which works on a 100% renewable scenario for 2050 in France, including all uses. Their moto is soberness, then efficiency, then renewables energy, I think this is close to your approach.

One of their major tricks to achieve 100% renewables is to convert the electricity into gas when there is oversupply. This way, they can use the existing gas network which is extensive and benefit from the 150 TWh of stockage already existing in France. Then they use it for heating and transportation and as a last resort to produce again electricity via cogeneration. This approach is quickly described in english in the summary of the last report https://negawatt.org/IMG/pdf/negawatt-scenario-2017-2050_english-summary.pdf
and better detailed in the 2011 report :
https://negawatt.org/IMG/pdf/150622_negawatt-executivesummary.pdf

I think this solution may be additional to the other solutions described in the article and besides on the website (reduction and flexibility of demand), and I am really looking forward to the next article.

Fusion

(28)

Has no one considered the impact of removing "global" scale energy from the atmosphere or the oceans? If you think climate change is a problem now, you have no imagination.

trylogic

(29)

“This means that up to ten times more solar panels and wind turbines need to be manufactured. The energy that's needed to create this infrastructure would make the switch to renewable energy self-defeating.”

“The energy that's saved on fuel is spent on the manufacturing, installation and interconnection of millions of solar panels and wind turbines.”

"...because the energy payback times of solar panels and wind turbines would increase six- or ten-fold.”


The statements above are incorrect for the following reasons :

If the energy needed for the manufacturing, installation and interconnection of millions of solar panels and wind turbines is CREATED by SOLAR PANELS and WIND TURBINES the payback time is ZERO!


For example :

A large industrial building has the roof covered with solar panels providing enough energy to manufacture the solar panels below.

Only solar and wind power is used for the manufacturing of components, installations and connections.

QED!

Wim Turkenburg

(30)

One question is whether we should focus on 100% renewables or even 100% solar and wind, or on 100% reduction of CO2 emission from the energy sector within the period 2017-2050. I think to focus should be on emission reduction.

Then a question is: what is the optimum contribution of intermittent renewables and what technologies and approaches could compliment the intermittency of solar and wind in an optimal manner.

We did such a study focused on the electricity sector in Europe in the year 2050 using an hourly simulation model (PLEXOS) and assuming a need for 96% CO2 emission reduction. We simulated the power system with 40%, 60% and 80% penetration of renewables and we assessed 5 options to compliment intermittent renewables to achieve both a reliable supply and the lowest total system costs.

It was found that total system costs can be reduced by a combination of: (1) Demand response (DR); (2) natural gas-fired power plants with and without Carbon Capture and Storage (CCS); (3) increased interconnection capacity; (4) curtailment. It was found that electricity storage increases total system costs in all scenarios.

The charging costs and investment costs make storage relatively expensive, even projecting cost reductions of 40% for Compressed Air Energy Storage (CAES) and 70% for batteries compared to 2012.

For details see: A.S. Brouwer et al., 'Least-cost options for integrating intermittent renewables in low-carbon power systems', Applied Energy 161 (2016) 48-74.

drs

(31)

"Part of the problem is that we (the U.S.) waste so much energy. The average European uses about 60% of the energy of the average American"

That's somewhat misleading. Europeans generally enjoy a nicer climate than most Americans, either generally cooler (but not too cold) or warm but dry. Much of the US lives in climate ranging from hot and humid to sub-freezing temperatures. This will naturally lead to more energy use in heating and A/C. And if Americans relocated to the friendlier West Coast, we'd have to provide them with water and housing.

We Americans could use a lot less energy with better housing and with denser cities (walkable, electrified public transit), though of course building new buildings takes energy of its own. European gas taxes have fostered fewer and more efficient cars. But there is a basic climate difference, too.

drs

(32)

"Has no one considered the impact of removing "global" scale energy from the atmosphere or the oceans? If you think climate change is a problem now, you have no imagination."

Rather, we've looked at the numbers. Human power use is a tiny fraction of surface isolation, like one part in a thousand.

It's conceivable that mass use of wind would make more of a difference to wind patterns, but being worse than global warming is a high bar to clear.

John Puma

(33)

The opening sentence: "While the potential of wind and solar energy is more than sufficient to supply the electricity demand of industrial societies, these resources are only available intermittently."

OK, correct for what is says explicitly.

BUT the unmentioned follow-up is that current global electricity demand (usage) is only a fraction of the current global energy demand (usage).

So the problem is: can current non-electrical energy usage be converted to electrical substitutes (think airliners) or can "modern" consume-more-tomorrow-than-today society be convinced to use considerably less energy?

Verify your Comment

Previewing your Comment

This is only a preview. Your comment has not yet been posted.

Working...
Your comment could not be posted. Error type:
Your comment has been saved. Comments are moderated and will not appear until approved by the author. Post another comment

The letters and numbers you entered did not match the image. Please try again.

As a final step before posting your comment, enter the letters and numbers you see in the image below. This prevents automated programs from posting comments.

Having trouble reading this image? View an alternate.

Working...

Post a comment

Comments are moderated, and will not appear until the author has approved them.

Your Information

(Name is required. Email address will not be displayed with the comment.)


News & Links

Let's build our own internet

Travel

Fruit Walls

  • Fruit walls
  • Urban Farming in the 1600s
    From the 16th to the 20th century, urban farmers grew Mediterranean fruits and vegetables as far north as England and the Netherlands, using only renewable energy.

The Chinese Wheelbarrow

  • Chinese wheelbarrow
  • How to downsize a transport network: the Chinese wheelbarrow
    For being such a seemingly ordinary vehicle, the wheelbarrow has a surprisingly exciting history. This is especially true in the East, where it became a universal means of transportation for both passengers and goods, even over long distances.

Wood Gas Vehicles

  • Wood gas cars 2
  • Firewood in the Fuel Tank: Wood Gas Vehicles
    Wood gas cars are a not-so-elegant but surprisingly efficient and ecological alternative to their petrol (gasoline) cousins, whilst their range is comparable to that of electric cars.

Open Modular Hardware

  • Open modular hardware2
  • How to make everything ourselves: open modular hardware
    Consumer products based on an open modular system can foster rapid innovation, without the drawback of wasting energy and materials. The parts of an obsolete generation of products can be used to design the next generation, or something completely different.

Power from the Tap

  • Water motors
  • Power from the Tap: Water Motors
    Just before the arrival of electricity at the end of the 19th century, miniature water turbines were connected to the tap and could power any machine that is now driven by electricity.

Aerial Ropeways

Other Languages

  • Some articles have been translated into French, German, Spanish, Italian and Dutch. Find them here.